WO2013005273A1 - Base station and power control method - Google Patents

Abstract

The present invention is able to suppress deterioration in a user channel, and to render processing for cancelling the synchronization channel of a wireless terminal unnecessary. On the basis of transmission format information (FI) of a user channel that transmits user data to the wireless terminal, the SCH power control unit (16) of a base station controls the power of an SCH for the wireless terminal synchronizing with the base station. For example, the SCH power control unit (16) reduces the power of the SCH when it is determined by means of the transmission format information (FI) that the user channel has a high transmission rate. As a result, in the user channel, deterioration resulting from SCH interference is suppressed. Also, in the wireless terminal, processing for cancelling the SCH is rendered unnecessary.

Description

Base station and power control method

This case relates to a base station that performs wireless communication with a wireless terminal and its power control method.

In a W-CDMA (Wideband Code Division Multiple Access) communication system, a radio terminal such as a mobile phone synchronizes with a base station, so that the base station multiplexes a synchronization signal (SCH: Synchronization CHannel) with voice data or the like to perform radio communication. Sending to the terminal. In the W-CDMA communication system, orthogonal data is allocated to each of a plurality of user channels to transmit user data, and SCH is transmitted using a code that is non-orthogonal to these orthogonal codes. For this reason, even in an ideal propagation path, the user channel does not have zero interference from the SCH, and characteristic degradation occurs. Particularly in HSDPA (High Speed Downlink Packet Access), which is an extension of the W-CDMA communication method, when a transmission format with a high transmission rate is used, characteristic degradation becomes significant.

Therefore, some wireless terminals include an SCH canceller that cancels SCH from the user channel. For example, a RAKE receiver of a wireless terminal uses a plurality of delay devices to synchronize the timing of a plurality of signals received with a delay. Then, the RAKE receiver of the wireless terminal estimates the amplitude of the SCH to be received, and subtracts and combines the SCHs in the respective received signals having the same timing. Thereby, the radio | wireless terminal can acquire the user channel which canceled SCH. However, on the other hand, the processing amount of the wireless terminal increases.

Conventionally, in the W-CDMA communication system, a transmission power control system that can prevent a DCCH (Dedicated Control Channel) communication error in advance while preventing a steady increase in transmission power has been proposed ( For example, see Patent Document 1).

Conventionally, a transmission power control apparatus has been proposed in which interference between channels is suppressed in a cell search at the start of communication or handover, and a communication terminal can easily perform synchronization acquisition (for example, Patent Document 2). reference).

Furthermore, conventionally, a method for establishing synchronization of mobile stations in a mobile communication system with higher accuracy in which the influence of noise and interference has been reduced has been proposed (see, for example, Patent Document 3).

JP 2008-166882 A JP 2003-218788 A JP 2001-358635 A

As described above, the user channel has a problem that characteristic deterioration occurs due to the synchronization channel. Further, when the wireless terminal cancels the synchronization channel from the user channel, there is a problem that the processing amount increases.

This case has been made in view of these points, and aims to suppress degradation of the user channel due to the synchronization channel. It is another object of the present invention to provide a base station and a power control method that can eliminate the process of canceling the synchronization channel of the wireless terminal.

In order to solve the above problems, a base station that performs wireless communication with a wireless terminal is provided. The base station includes a control unit that controls the power of a synchronization channel for the wireless terminal to synchronize with the base station based on transmission format information of a user channel that transmits user data to the wireless terminal.

Also, in order to solve the above problems, a base station that performs wireless communication with a wireless terminal is provided. The base station includes a control unit that controls power of the user channel overlapping with a synchronization channel transmitted to the wireless terminal based on transmission format information of a user channel that transmits user data to the wireless terminal.

According to the disclosed apparatus and method, it is possible to suppress degradation of the user channel and eliminate the need for canceling the synchronization channel of the wireless terminal.
These and other objects, features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings which illustrate preferred embodiments by way of example of the present invention.

It is a block diagram of the base station which concerns on 1st Embodiment. It is a figure explaining the electric power control of SCH. It is the flowchart which showed operation | movement of the base station. It is a block diagram of the base station which concerns on 2nd Embodiment. It is a figure explaining the electric power control of SCH. It is a block diagram of the base station which concerns on 3rd Embodiment. It is a block diagram of the base station which concerns on 4th Embodiment. It is a block diagram of the base station which concerns on 5th Embodiment. It is a figure explaining the radio wave radiation of SCH. It is a block diagram of the base station which concerns on 6th Embodiment. It is a figure explaining the radio wave radiation of SCH. It is a block diagram of the base station which concerns on 7th Embodiment. It is a block diagram of the base station which concerns on 8th Embodiment. It is a block diagram of the base station which concerns on 9th Embodiment. It is a block diagram of the base station which concerns on 10th Embodiment. It is the figure which showed the hardware structural example of the base station.

Hereinafter, embodiments will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram of a base station according to the first embodiment. The base station shown in FIG. 1 performs wireless communication with a wireless terminal such as a mobile phone by the W-CDMA communication method, for example. As shown in FIG. 1, the base station includes error correction code units 11a and 11b, modulation units 12a to 12c, spread modulation units 13a to 13c, addition units 14 and 18, multipliers 15 and 17, SCH power control unit 16, A wireless unit 19 and an antenna 20 are provided. Although FIG. 1 shows an example in which two transmission bit sequences B1 and B2 are code-spread for radio transmission for explanation, three or more transmission bit sequences may be code-spread for radio transmission. That is, there may be three or more sets of error correction code units, modulation units, and spread modulation units.

The user channel transmission format information FI for wirelessly transmitting the transmission bit string B1 to the wireless terminal is input to the error correction coding unit 11a, the modulation unit 12a, the spread modulation unit 13a, and the SCH power control unit 16 illustrated in FIG. The transmission format information FI includes the coding rate, modulation scheme, and spreading factor of the user channel that wirelessly transmits the transmission bit string B1.

The user channel coding rate, modulation scheme, and spreading rate are managed by the scheduler. Therefore, the transmission format information FI is generated from information held by the scheduler.

The transmission bit string B1 that is wirelessly transmitted to the wireless terminal through the user channel is input to the error correction code unit 11a. The transmission format information FI is input to the error correction code unit 11a. The error correction code unit 11a performs error correction code processing on the input transmission bit string B1 at the coding rate included in the transmission format information FI.

The modulation unit 12a modulates the signal output from the error correction code unit 11a based on the modulation method included in the transmission format information FI. The modulation method is, for example, QPSK (Quadrature Phase Shift Keying) or 16QAM (Quadrature Amplitude Modulation).

The spread modulation unit 13a code spreads the signal output from the modulation unit 12a based on the spreading factor included in the transmission format information FI.
The information included in the transmission format information FI changes according to the communication status with the wireless terminal, for example. For example, if the state of the propagation path with the wireless terminal is good, the transmission format information FI is changed so that the transmission rate of the transmission bit string B1 is increased. Specifically, if the state of the propagation path with the wireless terminal is good, the coding rate is changed to a low value, and the modulation scheme is changed to a multi-value. Further, the diffusion rate is changed to be small. As a result, the transmission rate of the transmission bit string B1 is increased.

The transmission bit string B2 that is wirelessly transmitted to the wireless terminal through the user channel is input to the error correction code unit 11b. The error correction code unit 11b performs error correction code processing on the input transmission bit string B2. The transmission bit string B1 is a bit string transmitted to a wireless terminal of a certain user, and the transmission bit string B2 is a bit string wirelessly transmitted to a wireless terminal of another user.

The modulation unit 12b modulates the transmission bit string B2 that has been subjected to the error correction code processing by the error correction code unit 11b. The spread modulation unit 13b code spreads the signal output from the modulation unit 12b. The spread code of the spread modulation unit 13b is orthogonal to the spread code of the spread modulation unit 13a so that the transmission bit strings B1 and B2 do not interfere with each other.

Note that the transmission format information FI is not input to the error correction code unit 11b, the modulation unit 12b, and the spread modulation unit 13b. Therefore, the transmission rate of the transmission bit string B2 is constant.

The pilot pattern P is input to the modulation unit 12c. The modulation unit 12c modulates the input pilot pattern P. The spread modulation unit 13c code spreads the signal output from the modulation unit 12c.

The adding unit 14 adds the signals output from the spread modulation units 13a to 13c. The multiplier 15 code spreads the signal output from the adder 14 with the scramble code sc.
The SCH power control unit 16 controls the power of the SCH (SCH signal) based on the coding rate, modulation scheme, and spreading factor included in the transmission format information FI. For example, the SCH power control unit 16 calculates the transmission rate of the transmission bit string B1 from the coding rate, modulation scheme, and spreading factor included in the transmission format information FI. Then, the SCH power control unit 16 outputs the first coefficient to the multiplier 17 if the calculated transmission rate is equal to or less than a predetermined threshold, for example, and if the calculated transmission rate is greater than the predetermined threshold, A second coefficient smaller than 1 is output to the multiplier 17. That is, when the transmission rate of the transmission bit string B1 is changed to a high rate, the SCH power control unit 16 outputs a small coefficient to the multiplier 17 so that the SCH power becomes small. That is, the SCH power control unit 16 outputs a coefficient that is inversely proportional to the transmission rate to the multiplier 17.

In addition, although the case where there was one threshold value was demonstrated above, there may be multiple. That is, the SCH power control unit 16 can also control the SCH power in stages.
The multiplier 17 receives an SCH signal for the wireless terminal to synchronize with the base station shown in FIG. 1 and a coefficient output from the SCH power control unit 16. Multiplier 17 multiplies the input SCH signal by a coefficient and outputs the result to adder 18. That is, the power of the SCH signal is controlled by the coefficient output from the SCH power control unit 16 and output to the adding unit 18. Note that the SCH signal is code-spread with non-orthogonal spreading codes and spreading codes of transmission bit strings B1 and B2.

The adder 18 adds the signal output from the multiplier 15 and the signal output from the multiplier 17. That is, the adding unit 18 combines the user channel signal and the SCH signal.
The wireless unit 19 up-converts the frequency of the signal output from the adding unit 18 to RF (Radio Frequency), and wirelessly transmits it to the wireless terminal via the antenna 20.

FIG. 2 is a diagram illustrating SCH power control. FIG. 2 shows a radio frame transmitted from the base station to the radio terminal. As shown in FIG. 2, the radio frame is formed of a plurality of slots. The horizontal direction in FIG. 2 indicates time, and the vertical direction indicates transmission power. The shaded area shown in FIG. 2 indicates the transmission power of the SCH.

2 is an area where the transmission rate of the user channel is greater than a predetermined threshold. That is, the area D11 indicates an area having a higher transmission rate than the other areas of the radio frame shown in FIG.

As described above, the SCH power control unit 16 controls the SCH power to decrease when the transmission rate of the user channel increases. Therefore, in the area D11 in FIG. 2, the SCH power is smaller than in the other areas.

The SCH is code spread with a spreading code that is non-orthogonal to the user channel. For this reason, the user channel does not have zero interference from the SCH, and characteristic degradation occurs. In particular, in HSDPA, when a transmission format with a high transmission rate is used, characteristic deterioration becomes significant.

However, the base station in FIG. 1 reduces the power of the SCH when the user channel has a high transmission rate, as shown in a region D11 in FIG. Thereby, as for a user channel, the interference from SCH is suppressed and the characteristic degradation of the user channel in a radio | wireless terminal is suppressed. Further, since interference with the SCH is suppressed in the user channel, the wireless terminal can obtain a user channel with good characteristics without performing SCH cancellation processing. In the above description, the SCH power is reduced, but the SCH power may be zero.

FIG. 3 is a flowchart showing the operation of the base station. The operation shown in the flowchart can be executed by a processor such as a DSP or a CPU.
[Step S1] The SCH power control unit 16 of the base station inputs the transmission format information FI.

[Step S2] The SCH power control unit 16 calculates a transmission rate of data (transmission bit string B1) transmitted to the wireless terminal based on the transmission format information FI.
[Step S3] The SCH power control unit 16 determines whether or not the calculated transmission rate is greater than a predetermined threshold. If the calculated transmission rate is greater than the predetermined threshold, the SCH power control unit 16 proceeds to step S4. If the calculated transmission rate is equal to or lower than the predetermined threshold, the SCH power control unit 16 proceeds to step S5.

[Step S4] The SCH power control unit 16 outputs a coefficient for a high transmission rate to the multiplier 17. For example, the SCH power control unit 16 outputs a coefficient having a value smaller than the coefficient in step S5 described below to the multiplier 17, and controls the SCH power to be reduced.

[Step S5] The SCH power control unit 16 outputs a coefficient for a low transmission rate to the multiplier 17. Note that the SCH whose power is controlled in steps S4 and S5 is wirelessly transmitted to the wireless terminal by the wireless unit 19.

As described above, the base station controls the SCH power for the wireless terminal to synchronize with the base station based on the transmission format information of the user channel for transmitting user data to the wireless terminal. Thereby, the base station can suppress the degradation of the user channel and can eliminate the SCH cancellation process of the wireless terminal.

In the above description, an example is shown in which one user's transmission bit string B1 is spread and wirelessly transmitted with one spreading code. However, a multicode that wirelessly transmits a plurality of one user's transmission bit strings with a plurality of spreading codes It can also be applied to transmission. In this case, the transmission format information FI includes the number of multicodes, and the SCH power control unit 16 calculates a coefficient for controlling the SCH power based on the number of multicodes included in the transmission format information FI. For example, as the number of multicodes increases, the transmission rate increases, so the SCH power control unit 16 decreases the coefficient.

[Second Embodiment]
Next, a second embodiment will be described in detail with reference to the drawings. In the second embodiment, the SCH average power is controlled to be constant.

FIG. 4 is a block diagram of a base station according to the second embodiment. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.
In FIG. 4, the base station includes a transmission format information generation unit 31 and an SCH power control unit 32. Transmission format schedule information FIS is input to transmission format information generation unit 31 and SCH power control unit 32.

The transmission format of the user channel is determined in advance by the scheduler before user data is transmitted. Therefore, the SCH power control unit 32 can know the future transmission format (transmission format information FI) from the transmission format schedule information FIS determined before data transmission.

The transmission format schedule information FIS includes a coding rate, a modulation method, and a spreading rate of data to be transmitted wirelessly. The transmission format information generation unit 31 generates transmission format information FI including these pieces of information included in the transmission format schedule information FIS, and outputs the transmission format information FI to the error correction coding unit 11a, the modulation unit 12a, and the spread modulation unit 13a. That is, the transmission format information generation unit 31 delays the coding rate, modulation method, and spreading factor included in the transmission format schedule information FIS so that the timing matches the transmission bit string B1 that is wirelessly transmitted. Output as information FI.

The SCH power control unit 32 receives transmission format schedule information FIS. Accordingly, the SCH power control unit 32 can know the transmission format information of the data at a timing before the data is wirelessly transmitted. That is, the SCH power control unit 32 can know the transmission rate of data before the data is wirelessly transmitted.

The SCH power control unit 32 calculates in advance the transmission rate of data to be wirelessly transmitted based on the coding rate, modulation scheme, and spreading factor included in the transmission format schedule information FIS. The SCH power control unit 32 calculates a coefficient for controlling the SCH power in advance based on the transmission rate calculated in advance.

The SCH power control unit 32 calculates the SCH coefficient of the slot before the slot to decrease the SCH power when the coefficient for decreasing the SCH power is calculated in advance. The SCH power control unit 32 calculates a coefficient for increasing the power of the SCH so that the average power of the SCH becomes constant.

Also, when the SCH power control unit 32 previously calculates a coefficient for reducing the power of the SCH, the SCH power control unit 32 calculates the coefficient of the SCH in the slot after the slot for reducing the power of the SCH. The SCH power control unit 32 calculates a coefficient for increasing the power of the SCH so that the average power of the SCH becomes constant.

FIG. 5 is a diagram illustrating SCH power control. FIG. 5 shows a radio frame transmitted from the base station to the radio terminal. As shown in FIG. 5, the radio frame is formed of a plurality of slots. The horizontal direction in FIG. 5 indicates time, and the vertical direction indicates transmission power. The shaded area shown in FIG. 5 indicates the SCH transmission power.

A radio frame area D21 shown in FIG. 5 indicates an area where the transmission rate of the user channel is larger than a predetermined threshold. That is, the area D21 indicates an area having a higher transmission rate than the other areas of the radio frame illustrated in FIG.

As described above, when the transmission rate of the user channel increases, the SCH power control unit 32 controls the SCH power to be reduced so that the interference of the SCH to the user channel is suppressed. Therefore, in region D21 in FIG. 5, the power of SCH is smaller than in other regions.

Further, the SCH power control unit 32 can calculate the transmission rate of the area D21 in advance based on the transmission format schedule information FIS, and can know the SCH power of the area D21. The SCH power control unit 32 also controls the SCH power in slots before and after the region D21 so that the average SCH power is constant. For example, the SCH power control unit 32 calculates the coefficient so that the SCH power in the regions D22 and D23 increases. As a result, the average power of the SCH is constant.

If the power of the SCH is reduced, the cell search performance of the wireless terminal may be affected. Normally, since cell search of a wireless terminal averages several frames of SCH, if the average SCH power is maintained, the influence on cell search performance is small. In the base station of FIG. 4, when the SCH power is lowered as shown in the region D21 of FIG. 5, the SCH power is increased in the regions D22 and D23 before and after the SCH power, and the average power of the SCH is controlled to be constant. . Accordingly, the base station in FIG. 4 can suppress the influence on the cell search performance of the radio terminal, suppress the degradation of the user channel, and can eliminate the SCH canceling process of the radio terminal.

In FIG. 5, the SCH power control unit 32 controls the power of both the SCH before and after the SCH power is controlled to be small, but may control the power of one SCH. For example, the SCH power control unit 32 may control only the SCH power in the region D22 such that the average SCH power is constant.

In this way, the base station controls the SCH power so that the average SCH power is constant. Accordingly, the base station can suppress the degradation of the user channel while suppressing the influence on the cell search performance of the wireless terminal, and can eliminate the need for the SCH canceling process of the wireless terminal.

[Third Embodiment]
Next, a third embodiment will be described in detail with reference to the drawings. DC-HSDPA (Dual Cell HSDPA) has been formulated as an extension of the W-CDMA communication system. In this method, a base station generates W-CDMA signals in two bands, and a wireless terminal receives both of them to improve the transmission rate. In the third embodiment, a case of DC-HSDPA will be described.

FIG. 6 is a block diagram of a base station according to the third embodiment. The base station shown in FIG. 6 performs wireless communication with a wireless terminal using a DC-HSDPA communication method. That is, the base station in FIG. 6 transmits data to the wireless terminal in two bands. 6, the same components as those in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted.

The base station shown in FIG. 6 has a transmission unit 41 and an SCH power control unit 42. The transmission unit 41 includes the error correction code units 11a and 11b, the modulation units 12a to 12c, the spread modulation units 13a to 13c, the addition units 14 and 18, the multipliers 15 and 17, the SCH power control unit 16, the wireless communication unit shown in FIG. The unit 19 and the antenna 20 are included.

The transmission bit string B11 is input to the error correction code unit 11a of the transmission unit 41, and the transmission bit string B12 is input to the error correction code unit 11b. Transmission format information FI1 is input to error correction coding unit 11a, modulation unit 12a, spread modulation unit 13a, and SCH power control unit 16 of transmission unit 41. The pilot pattern P is input to the modulation unit 12 c of the transmission unit 41.

The transmission bit strings B1 and B11 are transmitted to a wireless terminal of a certain user, and the transmission bit strings B2 and B12 are transmitted to a wireless terminal of another user. Each of the transmission bit sequences B1 and B11 is wirelessly transmitted to a wireless terminal of a certain user in a different band by the wireless unit 19 and the wireless unit 19 included in the transmission unit 41, and each of the transmission bit sequences B2 and B12 is transmitted to the wireless unit 19 Wireless transmission is performed to a wireless terminal of another user in a different band depending on the wireless unit 19 included in the transmission unit 41.

SCH power control information output from the SCH power control unit 16 of the transmission unit 41 is input to the SCH power control unit 42. The SCH power control information is information indicating whether or not the SCH power control unit 16 performs power control (whether or not the SCH power is reduced).

The SCH power control unit 42 has the same function as the SCH power control unit 32 described in FIG. However, the SCH power control unit 42 does not perform SCH average power control when the SCH power control information indicating that power control is not being performed is output from the SCH power control unit 16 of the transmission unit 41.

For example, when SCH power control information indicating that power control is not performed is output from the SCH power control unit 16 of the transmission unit 41, the SCH power control unit 42 does not perform the SCH power control illustrated in FIG. SCH power control shown in FIG. 2 is performed. In other words, when the SCH power control unit 16 of the transmission unit 41 controls the SCH power to be reduced, the SCH power control unit 42 controls the SCH power so that the average power of the SCH is constant. To do.

In the base station shown in FIG. 6, the SCH is also transmitted to the wireless terminal in a different band. Therefore, the wireless terminal only needs to detect the SCH of one band (for example, the SCH of the transmission unit 41). Therefore, if the power of the SCH transmitted in one band is not controlled to be small, the wireless terminal has a reduced power of the SCH transmitted in the other band (for example, the SCH controlled by the SCH power control unit 42). Even so, the cell search performance degradation is small. That is, the base station can suppress the cell terminal performance degradation of the radio terminal without controlling the SCH average power constant in the other band.

On the other hand, if the power of the SCH transmitted in one band is controlled to be small, if the average power of the SCH transmitted in the other band decreases, the cell search performance degradation may be affected. . Therefore, in this case, the SCH power control unit 42 controls the SCH power so that the average power of the SCH is constant.

As described above, the SCH power control unit 42 controls the average power of the SCH according to the SCH power control of the SCH power control unit 16 included in the transmission unit 41. Accordingly, the base station can suppress the degradation of the user channel while suppressing the influence on the cell search performance of the wireless terminal, and can eliminate the need for the SCH canceling process of the wireless terminal.

[Fourth Embodiment]
Next, a fourth embodiment will be described in detail with reference to the drawings. In the fourth embodiment, SCH power control when the base station retransmits data will be described.

FIG. 7 is a block diagram of a base station according to the fourth embodiment. 7, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 7, the base station includes an ARQ (Automatic Repeat reQuest) control unit 51 and an SCH power control unit 52.

In HSDPA, when a wireless terminal detects an error in received data, it makes a retransmission request for that data to the base station. When the wireless terminal receives the retransmission data from the base station, the wireless terminal combines with the initial transmission data to improve the SN (Signal Noise) ratio and perform reception processing. If the state of the propagation path does not change much at the time of initial transmission and retransmission of data, the S / N ratio is improved about twice.

Compared with the improvement of the SN ratio, the degradation of the user channel due to SCH interference is small. That is, even if the SCH power is not controlled to be small when retransmitting data at a high transmission rate, the degradation of the received data of the wireless terminal is small. Therefore, the base station in FIG. 7 does not perform SCH power control when data is retransmitted.

The ARQ control unit 51 performs data retransmission control. For example, the ARQ control unit 51 performs data retransmission processing in response to a data retransmission request from a wireless terminal. When retransmitting data, the ARQ control unit 51 outputs retransmission information indicating that the data is retransmitted to the SCH power control unit 52.

The SCH power control unit 52 has the same function as the SCH power control unit 16 described in FIG. However, when retransmission information indicating that data is retransmitted is output from the ARQ control unit 51, the SCH power control unit 52 sets a coefficient for performing SCH power control even if the transmission rate of the user channel is a high transmission rate. It does not change. That is, the SCH power control unit 52 does not control the SCH power to be reduced even when the retransmission data has a high transmission rate.

In this way, the base station does not change the SCH power when the user channel is retransmitted. Accordingly, the base station can suppress the degradation of the user channel while suppressing the influence on the cell search performance of the wireless terminal, and can eliminate the need for the SCH canceling process of the wireless terminal.

[Fifth Embodiment]
Next, a fifth embodiment will be described in detail with reference to the drawings. In the fifth embodiment, a case where a base station transmits data using a plurality of antennas will be described.

FIG. 8 is a block diagram of a base station according to the fifth embodiment. 8, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 8, the base station includes error correction code sections 61a and 61b, modulation sections 62a to 62c, spread modulation sections 63a to 63c, addition sections 64 and 67, multipliers 65 and 66, radio section 68, antenna 69, and SCH. A power control unit 70 is included.

As shown in FIG. 8, the transmission bit string B1 input to the error correction code unit 11a is input to the error correction code unit 61a. The transmission bit string B2 input to the error correction code unit 11b is input to the error correction code unit 61b. The pilot pattern P input to the modulation unit 12c is input to the modulation unit 62c. Further, transmission format information FI input to the error correction code unit 11a, the modulation unit 12a, and the spread modulation unit 13a is input to the error correction code unit 61a, the modulation unit 62a, and the spread modulation unit 63a. In the following, the error correction code units 11a and 11b, the modulation units 12a to 12c, the spread modulation units 13a to 13c, the addition units 14 and 18, the multipliers 15 and 17, the radio unit 19, and the antenna 20 are referred to as a first transmission block. The error correction code units 61a and 61b, the modulation units 62a to 62c, the spread modulation units 63a to 63c, the addition units 64 and 67, the multipliers 65 and 66, the radio unit 68, and the antenna 69 are referred to as a second transmission block. Sometimes.

The first transmission block is the same as each unit described in FIG. 1, and each unit of the second transmission block has the same function as the corresponding unit of the first transmission block. Description of the transmission block is omitted.

The base station in FIG. 8 outputs the transmission bit strings B1 and B2, the SCH signal, and the pilot signal simultaneously in the same band by the two antennas 20 and 69. The radio terminal performs demodulation by separating these signals transmitted at the same time.

When the base station has a plurality of antennas, it can deflect the radiation of the radio wave output from each antenna by controlling the power of each antenna. Therefore, the SCH power control unit 70 controls the SCH power output from the antennas 20 and 69 to deflect the SCH radio wave radiation and change the SCH power received by the wireless terminal.

The SCH power control unit 70 has the same function as the SCH power control unit 16 described in FIG. However, the SCH power control unit 70 changes the coefficient output to each of the multipliers 17 and 66 based on the transmission format information FI. That is, the SCH power control unit 70 changes the SCH power output from each of the antennas 20 and 69.

For example, the SCH power control unit 70 calculates the transmission rate of the transmission bit string B1 based on the transmission format information FI. The SCH power control unit 70 changes the coefficient output to the multipliers 17 and 66 when the calculated transmission rate of the transmission bit string B1 is, for example, a high transmission rate, and the SCH radio wave output from the antennas 20 and 69. Deflects radiation. Then, the SCH power control unit 70 reduces the power of the SCH received by the wireless terminal that receives the transmission bit string B1. That is, the SCH power control unit 70 adds weights to the SCHs corresponding to the antennas 20 and 69, deflects the SCH radio wave radiation output from the antennas 20 and 69, and reduces the SCH power received by the wireless terminal. Like that.

The coefficient output from the SCH power control unit 70 is, for example, a complex number. The SCH power control unit 70 changes the amplitude and phase of the SCH by the complex coefficient, and deflects the radio wave radiation of the SCH.

FIG. 9 is a diagram for explaining SCH radio wave radiation. FIG. 9A shows SCH radio emission when the transmission rate of the transmission bit string B1 is a low transmission rate. FIG. 9B shows SCH radio emission when the transmission rate of the transmission bit string B1 is a high transmission rate. Radiations E11 to E13 shown in FIGS. 9A and 9B indicate SCH radio wave radiation. 9A and 9B show the antennas 20 and 69 shown in FIG.

Here, as an example, the position of a wireless terminal built in a vending machine can be known in advance. Hereinafter, the wireless terminal that receives the transmission bit string B1 is referred to as a vending machine. The crosses shown in FIGS. 9A and 9B indicate the position of the vending machine that receives the transmission bit string B1.

The SCH power control unit 70 does not lower the SCH power when the transmission rate of the transmission bit string B1 transmitted to the vending machine is a low transmission rate. In this case, the SCH power control unit 70 outputs the coefficients to the multipliers 17 and 66 so that the SCH radio waves are radiated in all directions, as shown in FIG.

For example, if a radio wave is output from only one of the antennas 20 and 69, the radio wave is radiated in all directions. Therefore, for example, the SCH power control unit 70 sets the coefficient output to one of the multipliers 17 and 66 to zero so that the SCH radio wave radiation is indicated by the radiation E11 in FIG. 9A. be able to.

The SCH power control unit 70 reduces the SCH power when the transmission rate of the transmission bit string B1 transmitted to the vending machine is a high transmission rate. In this case, the SCH power control unit 70 outputs the coefficients to the multipliers 17 and 66 so that the SCH radio wave is deflected and radiated as indicated by the radiation E12 and E13 in FIG. That is, the SCH power control unit 70 deflects the SCH radio wave radiation so that the power of the SCH at the position where the vending machine is present is reduced, thereby reducing the power of the SCH received by the vending machine. Thereby, the vending machine suppresses the interference by the SCH of the user channel.

Thus, the base station adds weights to the SCHs output to the plurality of antennas 20 and 69 so that the SCH radio wave radiation is deflected. Thereby, the base station can suppress the degradation of the user channel and can eliminate the SCH cancellation process of the wireless terminal.

[Sixth Embodiment]
Next, a sixth embodiment will be described in detail with reference to the drawings. In the sixth embodiment, a case will be described in which a base station precodes and transmits a user channel.

FIG. 10 is a block diagram of a base station according to the sixth embodiment. 10, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 10, the base station includes precoding units 81 and 84, error correction code unit 82, modulation unit 83, spread modulation unit 85, addition units 86 and 88, multipliers 87 and 92, radio unit 89, antenna 90, and An SCH power control unit 91 is included.

The transmission bit string B1 input to the error correction code unit 11a is input to the error correction code unit 82. Further, the transmission format information FI is input to the error correction code unit 82. The modulation unit 83, the spread modulation unit 85, the addition units 86 and 88, the multiplier 87, the radio unit 89, and the antenna 90 are the modulation unit 12a, the spread modulation unit 13a, the addition units 14 and 18, the multiplier 15, and the radio unit 19. , And the antenna 20, and the description thereof is omitted.

The transmission format information FI is input to the precoding units 81 and 84. The transmission format information FI includes a precoding coefficient. The precoding units 81 and 84 precode the signals output from the modulation units 12a and 83 by multiplying the signals by the precoding coefficient included in the transmission format information FI.

The information for calculating the precoding coefficient is transmitted from the wireless terminal. For example, the coefficient calculation unit (not shown in FIG. 10) calculates the precoding coefficient based on the information received from the wireless terminal so that the received power of the user channel received by the wireless terminal is increased. Then, the coefficient calculation unit includes the calculated precoding coefficient in the transmission format information FI.

That is, the coefficient calculation unit calculates the weight (precoding coefficient) of the user channel transmitted by the plurality of antennas 20 and 90 based on feedback information from the wireless terminal, and includes it in the transmission format information FI. The precoding unit 81 adds weights included in the transmission format information FI to user channels transmitted by the plurality of antennas 20 and 90, and deflects radio wave radiation of the user channels output from the antennas 20 and 90. That is, the precoding units 81 and 84 deflect the radio wave radiation of the antennas 20 and 90 so that the reception power of the user channel of the wireless terminal is increased. In FIG. 10, the transmission bit string B1 is precoded, but the transmission bit string B2 may also be precoded.

The SCH power control unit 91 has the same function as the SCH power control unit 16 described in FIG. However, the SCH power control unit 91 changes the coefficient output to each of the multipliers 17 and 92 based on the precoding coefficient included in the transmission format information FI. That is, the SCH power control unit 91 changes the SCH power output from each of the antennas 20 and 90.

For example, the SCH power control unit 91 calculates the transmission rate of the transmission bit string B1 based on the coding rate, modulation scheme, and spreading factor included in the transmission format information FI. The SCH power control unit 91 calculates a coefficient to be output to the multipliers 17 and 92 based on the precoding coefficient included in the transmission format information FI when the calculated transmission rate of the transmission bit string B1 is, for example, a high transmission rate. The SCH radio wave radiation output from the antennas 20 and 90 is changed. For example, the SCH power control unit 91 calculates a coefficient for radio wave radiation orthogonal to precoding radio wave radiation, and outputs the coefficient to the multipliers 17 and 92. That is, the SCH power control unit 91 adds weighting to the SCH output from the antennas 20 and 90, and deflects the radio wave radiation of the SCH output from the antennas 20 and 90 to be orthogonal to the radio wave radiation of the user channel. The power of the SCH received by the wireless terminal is reduced.

The coefficient output from the SCH power control unit 91 is, for example, a complex number. The SCH power control unit 91 changes the amplitude and phase of the SCH according to the complex coefficient, and deflects the radio wave radiation of the SCH.

FIG. 11 is a diagram for explaining SCH radio wave radiation. A solid line radiation E21 shown in FIG. 11 indicates radio wave radiation of the user channel. A dotted line radiation E22 indicates SCH radio wave radiation. The crosses shown in FIG. 11 indicate the position of the wireless terminal that receives the transmission bit string B1.

The radio wave radiation of the user channel received by the wireless terminal is formed so as to increase its power by precoding. For example, radio wave radiation of the user channel received by the wireless terminal is as indicated by radiation E21.

The SCH power control unit 91 controls the SCH power to be small when the transmission rate of the transmission bit string B1 is a high transmission rate. The SCH power control unit 91 can control the radiation of the SCH as indicated by the radiation E22 by calculating a coefficient orthogonal to the precoding coefficient and outputting the coefficient to the multipliers 17 and 92. That is, the SCH power control unit 91 deflects the SCH radio wave radiation based on the precoding coefficient of the user channel so that the SCH power at the position where the wireless terminal exists is reduced.

As described above, information for calculating the precoding coefficient is fed back from the wireless terminal. Accordingly, the precoding units 81 and 84 can control the power of the user channel at the position where the mobile terminal exists even if the wireless terminal moves. Since the SCH power control unit 91 deflects the SCH radio wave radiation based on the feedback precoding coefficient, the SCH power control unit 91 reduces the SCH power at the position where the mobile terminal exists even if the mobile terminal moves. Can be controlled. Thereby, even if the wireless terminal moves, interference due to the SCH of the user channel is suppressed.

As described above, the base station adds weights to the SCHs output to the plurality of antennas 20 and 69 so that the radio wave radiation of the SCH is orthogonal to the radio wave radiation of the user channel. Thereby, even if a radio terminal moves, the base station can suppress degradation of the user channel and can eliminate the SCH cancellation process of the radio terminal.

[Seventh Embodiment]
Next, a seventh embodiment will be described in detail with reference to the drawings. In the seventh embodiment, a case will be described in which SCH power control is performed depending on whether a wireless terminal includes an SCH canceller that cancels SCH.

FIG. 12 is a block diagram of a base station according to the seventh embodiment. 12, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 12, the base station includes an uplink signal reception unit 101, a type information generation unit 102, and an SCH power control unit 103.

The uplink signal receiving unit 101 receives an uplink signal from a wireless terminal. Based on the uplink signal received by the uplink signal receiving unit 101, the type information generating unit 102 generates type information indicating whether the wireless terminal that has transmitted the uplink signal has an SCH canceller.

For example, after establishing a communication link with a base station, a wireless terminal that does not have an SCH canceller transmits information to the base station that it does not have an SCH canceller. The type information generation unit 102 generates type information indicating that the SCH canceller is not included, based on the information (uplink signal) received by the uplink signal receiving unit 101 indicating that the SCH canceller is not included.

The SCH power control unit 103 has the same function as the SCH power control unit 16 described in FIG. However, the SCH power control unit 103 outputs a coefficient for controlling the SCH power to the multiplier 17 based on the type information output from the type information generation unit 102.

For example, it is assumed that the wireless terminal that receives the transmission bit string B1 does not have an SCH canceller. In this case, the type information output from the type information generation unit 102 indicates that no SCH canceller is provided, and the SCH power control unit 103 outputs a coefficient for controlling the power of the SCH to the multiplier 17. On the other hand, it is assumed that the wireless terminal that receives the transmission bit string B1 has an SCH canceller. In this case, the SCH power control unit 103 does not output a coefficient for controlling the SCH power to the multiplier 17.

In this way, the base station controls the power of the SCH for the wireless terminal that does not have the SCH canceller, and the power of the synchronization channel for the wireless terminal that cancels the SCH and extracts the user channel. I tried not to change. Thereby, the base station can suppress the influence of the cell search due to the SCH power change of the wireless terminal.

[Eighth Embodiment]
Next, an eighth embodiment will be described in detail with reference to the drawings. In W-CDMA, the base station transmits P-SCH (Primary SCH) for synchronizing slot timing and S-SCH (Secondary SCH) for synchronizing frame timing to the radio terminal as SCH. ing. In the eighth embodiment, a case will be described in which power control is performed on the SCH P-SCH.

FIG. 13 is a block diagram of a base station according to the eighth embodiment. In FIG. 13, the same components as those in FIG.
In the base station of FIG. 13, a multiplier 17 receives a P-SCH signal. Further, the S-SCH signal is input to the adding unit 18. Therefore, in the base station of FIG. 13, the P-SCH is power controlled by the SCH power control unit 16, and the S-SCH is not power controlled. The P-SCH and S-SCH are combined by the adding unit 18 and wirelessly transmitted to the wireless terminal by the wireless unit 19.

P-SCH transmits the same code in each slot. On the other hand, the S-SCH transmits a different code for each slot and transmits information using a code pattern for one frame. Therefore, the average power of the P-SCH affects the detection performance of the code pattern, and the power of each slot of the S-SCH affects the detection performance of the code pattern even if the average power is constant. Therefore, the SCH power control unit 16 controls the power of the P-SCH and does not control the power of the S-SCH. That is, the SCH power control unit 16 controls part of the power of the plurality of types of SCHs.

In this way, the base station controls part of the power of multiple types of SCH. Thereby, the base station can suppress the influence of the cell search due to the power change of some SCHs, and can suppress the degradation of the user channel due to interference of other SCHs.

In the above description, the S-SCH power is made constant. However, the S-SCH power may be controlled to change. For example, the SCH power control unit 16 changes the S-SCH power to be smaller than the P-SCH power change so as not to be affected by the S-SCH cell search. As a result, the base station can also suppress the influence of interference due to the P-SCH of the user channel of the wireless terminal.

[Ninth Embodiment]
Next, a ninth embodiment will be described in detail with reference to the drawings. In the above, paying attention to transmission format information (transmission rate) of a certain user, the interference due to SCH of the user channel of the user is suppressed. 9th Embodiment demonstrates the case where the interference by SCH of the user channel of a some user is suppressed.

FIG. 14 is a block diagram of a base station according to the ninth embodiment. 14, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.
In FIG. 14, for example, the transmission rate is varied in the transmission bit strings B1 to B3 of a plurality of users A, B, and C. Transmission format information FI1 is input to the error correction code unit 11a, the modulation unit 12a, and the spread modulation unit 13a. Transmission format information FI2 is input to the error correction code unit 11b, the modulation unit 12b, and the spread modulation unit 13b. Transmission format information FI3 is input to error correction coding unit 11d, modulation unit 12d, and spread modulation unit 13d. The operations of the error correction code units 11b and 11d, the modulation units 12b and 12d, and the spread modulation units 13b and 13d are the same as those of the error correction code unit 11a, the modulation unit 12a, and the spread modulation unit 13a described in FIG. The description is omitted.

The SCH power control unit 111 receives transmission format information FI1 to FI3. The SCH power control unit 111 controls the SCH power based on the coding rate, modulation scheme, and spreading factor included in the transmission format information FI.

For example, the SCH power control unit 111 transmits each of the transmission bit sequences B1 to B3 from the coding rate, modulation scheme, and spreading factor of the transmission bit sequences B1 to B3 included in each of the transmission format information FI1 to FI3. Calculate the rate. Then, the SCH power control unit 111 adds the calculated transmission rates, and outputs the first coefficient to the multiplier 17 if the added transmission rate is, for example, a predetermined threshold value or less. Further, if the added transmission rate is larger than a predetermined threshold, SCH power control section 111 outputs a second coefficient smaller than the first coefficient to multiplier 17. That is, when the transmission rate obtained by adding the transmission bit strings B1 to B3 is changed to a high transmission rate, the SCH power control unit 111 multiplies a small coefficient so that the SCH power becomes small.

As described above, the base station controls the SCH power based on the transmission format information FI1 to FI3 of the user channels of a plurality of wireless terminals. Thereby, the base station can suppress degradation of user channels of a plurality of wireless terminals and can eliminate the need for SCH cancellation processing of the wireless terminals.

[Tenth embodiment]
Next, a tenth embodiment will be described in detail with reference to the drawings. In the above description, the SCH power is controlled based on the transmission format information of the user channel. In the tenth embodiment, the power of the SCH is made constant and the power of the user channel is controlled.

FIG. 15 is a block diagram of a base station according to the tenth embodiment. 15 that are the same as those in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.
The base station in FIG. 15 does not have the SCH power control unit 16 described in FIG. In the base station of FIG. 15, the SCH signal is input to the adder 18 without power control.

The base station in FIG. 15 has a power control unit 121 and a multiplier 122. The power control unit 121 controls the power of the user channel of the transmission bit string B1 based on the transmission format information of the transmission bit string B1. The power control unit 121 controls the power of the user channel of the transmission bit string B1 in the user channel region overlapping with the SCH. For example, the power control unit 121 controls the power of the user channel in the region overlapping the shaded portion shown in FIG.

The power control unit 121 calculates the transmission rate of the transmission bit string B1 from, for example, the coding rate, the modulation scheme, and the spreading factor included in the transmission format information FI. Then, the power control unit 121 outputs the first coefficient to the multiplier 122 if the calculated transmission rate is equal to or less than a predetermined threshold, for example, and if the calculated transmission rate is greater than the predetermined threshold, the first The second coefficient larger than the first coefficient is output to the multiplier 122. That is, when the transmission rate of transmission bit string B1 is changed to a high rate, power control unit 121 outputs a large coefficient to multiplier 122 so that the power of the user channel is increased. That is, the power control unit 121 outputs a coefficient proportional to the transmission rate to the multiplier 122. Thereby, the influence of interference by SCH is suppressed in the user channel.

A coefficient output from the power control unit 121 is input to the multiplier 122. The multiplier 122 multiplies the signal output from the spread modulation unit 13 a by the coefficient and outputs the result to the addition unit 14. That is, the transmission bit string B <b> 1 is controlled in power by the coefficient output from the power control unit 121 and output to the addition unit 14.

As described above, the base station controls the power of the user channel in the area overlapping with the synchronization channel transmitted to the wireless terminal based on the transmission format information of the user channel transmitting user data to the wireless terminal. Thereby, the base station can suppress the degradation of the user channel and can eliminate the SCH cancellation process of the wireless terminal.

Note that the second to ninth embodiments can also be applied to control the power of the user channel.
Also, the first embodiment to the tenth embodiment can be combined. For example, the control of constant SCH average power described in the second embodiment and the SCH weighting control by precoding transmission described in the sixth embodiment are combined, or described in the first embodiment. SCH power control and the user channel described in the tenth embodiment may be combined.

Hereinafter, the hardware configuration of the base station will be described.
FIG. 16 is a diagram illustrating a hardware configuration example of the base station. As illustrated in FIG. 16, the base station includes a CPU (Central Processing Unit) 131, a DSP (Digital Signal Processing) 132, a memory 133, a radio unit 134, and a bus 135. A DSP 132, a memory 133, and a wireless unit 134 are connected to the CPU 131 via a bus 135 to control the entire apparatus.

The memory 133 stores an OS (Operating System) program and application programs executed by the CPU 131 and the DSP 132. The memory 133 stores various data necessary for processing by the CPU 131 and the DSP 132.

The wireless unit 134 performs wireless communication with a wireless terminal. For example, the wireless unit 134 performs D / A (Digital-to-Analog) conversion on the digital signal processed by the CPU 131 and the DSP 132, up-converts the frequency of the D / A converted signal, and transmits the converted signal to the wireless terminal. Further, the wireless unit 134 down-converts the frequency of the signal received from the wireless terminal, for example, and performs A / D (Analog-to-Digital) conversion. The A / D converted signal is subjected to predetermined processing by the CPU 131 and the DSP 132.

The functions of the units described in the first to tenth embodiments can be realized by the CPU 131 and the DSP 132, for example. However, the radio unit described in the first to tenth embodiments is realized by the radio unit 134.

Also, the functions of the units described in the first to tenth embodiments can be realized by, for example, dedicated hardware. For example, the function can be realized by FPGA (Field Programmable Gate Gate Array).

The above merely shows the principle of the present invention. In addition, many modifications and changes can be made by those skilled in the art, and the present invention is not limited to the precise configuration and application shown and described above, and all corresponding modifications and equivalents may be And the equivalents thereof are considered to be within the scope of the invention.

11a, 11b Error correcting code unit 12a-12c Modulating unit 13a-13c Spreading modulation unit 14, 18 Adder unit 15, 17 Multiplier 16 SCH power control unit 19 Radio unit 20 Antenna

Claims (12)

1. In a base station that performs wireless communication with a wireless terminal,
   A control unit for controlling power of a synchronization channel for the wireless terminal to synchronize with the base station based on transmission format information of a user channel for transmitting user data to the wireless terminal;
   A base station characterized by comprising:
2. The base station according to claim 1, wherein the control unit controls the power of the synchronization channel so that an average power of the synchronization channel is constant.
3. A transmitter that wirelessly transmits the synchronization channel at a plurality of frequencies;
   A plurality of the control units are provided corresponding to the plurality of frequencies,
   One of the control units controls the power of the synchronization channel so that an average power of the synchronization channel is constant when another control unit performs power control of the synchronization channel. The base station according to claim 2.
4. The base station according to claim 1, wherein the control unit does not change power of the synchronization channel when the user channel is retransmitted.
5. A plurality of antennas;
   The base station according to claim 1, wherein the control unit adds weighting to the synchronization channel output to the plurality of antennas such that radio wave radiation of the synchronization channel is deflected.
6. A plurality of antennas;
   The base station according to claim 1, wherein the control unit adds weighting to the synchronization channel so that the radio wave radiation of the synchronization channel is orthogonal to the radio wave radiation of the data channel.
7. The said control part does not change the electric power of the said synchronization channel with respect to the said radio | wireless terminal provided with the function which cancels the said synchronization channel and extracts the said user channel, The range of Claim 1 characterized by the above-mentioned. base station.
8. A transmitter that wirelessly transmits a plurality of types of the synchronization channels;
   The base station according to claim 1, wherein the control unit controls power of a part of the plurality of types of synchronization channels.
9. The base station according to claim 1, wherein the control unit controls power of the synchronization channel based on transmission format information of the user channel of a plurality of the wireless terminals.
10. In a base station that performs wireless communication with a wireless terminal,
    A control unit for controlling power of the user channel overlapping with a synchronization channel to be transmitted to the wireless terminal based on transmission format information of the user channel for transmitting user data to the wireless terminal;
    A base station characterized by comprising:
11. In a power control method of a base station that performs wireless communication with a wireless terminal,
    Based on transmission format information of a user channel that transmits user data to the wireless terminal, the wireless terminal controls the power of a synchronization channel for synchronizing with the base station,
    A power control method characterized by the above.
12. In a power control method of a base station that performs wireless communication with a wireless terminal,
    Based on transmission format information of a user channel that transmits user data to the wireless terminal, the power of the user channel that overlaps a synchronization channel that is transmitted to the wireless terminal is controlled.
    A power control method characterized by the above.

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